How did we make DeepSeek outperform Opus

ahmadawais

hey HN, sharing harness engineering deep dive on tool calling repairs for open models. i've been thinking about why "open model bad at tool calling" is almost always a harness problem, not a model problem. spent time looking at billions of tokens from DeepSeek (and other open models) in our coding agent. ended up building a tool-input repair layer on top of Zod. by the end, DeepSeek V4 Pro was beating Opus 4.7 in 6/10 of our internal evals. the main things that helped: - most failures came from a small set of recurring schema mistakes - switched from preprocess-then-validate to validate-then-repair - handled some weird cases like markdown auto-links leaking into file paths full writeup: https://x.com/MrAhmadAwais/status/2050956678502420612 video version (more detailed): https://www.youtube.com/watch?v=f61DCDwvFis

bel8

> he trigger was watching deepseek-flash fail on the simplest /review run, every shellCommand and readFile call bouncing back with a raw zod issues blob, the model unable to recover because the error wasn't in a form it could read. by the end deepseek v4 pro was beating opus 4.7 6/10 times on our internal evals. I think this is why Xiaomi forked OpenCode and created their own agent hardness, to reduce friction between model and harness: https://github.com/XiaomiMiMo/MiMo-Code